Electrophoretic deposition of bilayer composite films based on CoFe2O4 and Nb-doped PZT

The magnetoelectric (ME) composites with piezoelectric and magnetostrictive material are of interest in the smart manufacturing and mechatronics fields as actuators/transducers, sensors, antennas, filters, non-volatile memories, etc. Spinel cobalt ferrite (CFO), a highly magnetostrictive material and niobium-doped lead zirconate titanate (PZTN), a piezoelectric perovskite phase are chosen as constituent phases for ME composite. The production process is designed in order to avoid the chemical reaction between the piezoelectric and magnetostrictive materials, to prevent the formation of percolation chains of the magnetostrictive phase, and to maximize the mechanical coupling at the interface between the two phases. In this view, the electrophoretic deposition (EPD) is a low cost and flexible technique to shape nanoparticles into multilayered heterostructures. The combination of different materials by EPD, showing promising ME coupling, can be regarded as a useful, preliminary approach in the search of novel ME materials for many applications, potentially with great industrial and technological benefits. In this work, composite bilayer CFO/PZTN thick films were deposited on platinum coated alumina by EPD from ethanol-based colloidal suspensions. Good adhesion and compaction of the green film were achieved by optimization of deposition voltage and time, and high density of the film and minimized interphase reactions occurred after sintering. The chemical activity between the two layers was controlled through the batches composition and it could lead to the synthesis of complex engineered structures. The deposited volume, the mixing of dielectric and magnetic phases and the density and ordering of the films have been verified by electron scanning microscopy after heat treatment. The ferroelectric, piezoelectric and magnetic properties were tested on the sintered films.